Conventionally, contact type cards designed to read magnetically stored information have been mainly used as cards used for automatic ticket gate systems in railroads and entrance control systems in research laboratories and the like. Recently, however, non-contact type cards (IC cards and the like) have been likely to be used. An advantage of a non-contact type is that the user need not take out a commuter pass or card from a pocket or handbag. Even if the user needs to take out such a card from the bag, information can be read when he/she only holds up the card against a reading apparatus. There is no need to make the card pass through the apparatus. In addition, the time taken to read information can be shortened. Furthermore, wear in the card can be prevented. Moreover, a large amount of information can be stored in an IC card or the like.
As described above, a non-contact type card is excellent in operability and can store a large amount of information. On the other hand, information may be read out from the card at any moment. For example, as non-contact type cards are expected to become multifunctional more and more in the future, IC cards equipped with railroad commuter pass applications may also be equipped with credit card applications and the like. In this case, in addition to holder's names, station names, and validity terms, other important information (e.g., credit information) may be stored in non-contact type cards. If important information is stolen from such a non-contact type card, the holder cannot know when and where the information was stolen, and the information may be illicitly used before the holder knows it.